Publications on the WWW

• by R.A.Laing, A.H.Bridle, W.D.Cotton, D.M.Worrall and M.Birkinshaw
• to appear in "Extragalactic Jets: Theory and Observation from Radio to Gamma Ray", eds. T.A.Rector and D.S.De Young, ASP Conference Series
• Accurate imaging of radio spectral index for the inner jets in three FR I radio galaxies.
• Where jets first brighten, small dispersion around spectral index of 0.62 in region where bright X-ray emission is detected.
• Further from nucleus, spectral index flattens to 0.50 - 0.55 and X-ray emission fainter relative to radio.
• Brightest X-ray emission not associated with flattest radio spectra, but with particle-acceleration process whose characteristic energy index is 2.24.
• Change in spectral index occurs roughly where relativistic jet models require rapid deceleration.

• by R.A.Laing and A.H.Bridle
• to appear in "Extragalactic Jets: Theory and Observation from Radio to Gamma Ray", eds. T.A.Rector and D.S.De Young, ASP Conference Series
• Unequivocal evidence that the jets in FR I radio galaxies are initially relativistic, decelerating flows
• Mass entrainment -from stellar mass loss within the jet volume or via a boundary layer at the jet surface is the most likely cause for deceleration.
• Consistent with velocity field and geometry inferred from kinematic modelling and external gas density and pressure profiles derived from X-ray data. .
• Jets must initially be very light, perhaps with an electron-positron composition.

• by D.M.Worrall, M.Birkinshaw, R.A.Laing, W.D.Cotton and A.H.Bridle
• Monthly Notices of the Royal Astronomical Society, 380, 2-14 (2007)
• Deep imaging of the jet, nucleus and gaseous atmosphere of NGC315 with the Chandra X-ray observatory are compared with high-resolution VLA imaging at 5 GHz.
• Diffuse X-ray synchrotron emission is detected from the jet through regions both of fast bulk flow and deceleration. diffuse emission.
• The X-ray to radio ratio provides evidence for distributed particle acceleration throughout the fast moving region. .
• A remarkable knotty filament within the jet is seen in both the radio and the X-ray; its oscillatory apearance, roughly aligned magnetic field and requirements for particle acceleration suggest that it is a magnetic strand within a shear layer between fast inner and slower outer flow.

• by R.A.Laing, A.H.Bridle and J.R.Canvin
• to appear in "Relativistic Astrophysics and Cosmology: Einstein's Legacy", eds. B. Aschenbach, V. Burwitz, G. Hasinger, and B. Leibundgut, Springer-Verlag, 445-448 (2007)
• The largest-scale manifestation of Special Relativistic aberration in contemporary astrophysics is the appearance of initial asymmetries in kpc-scale radio-galaxy jets. We discuss how the Doppler beaming and Special Relativistic aberration modify the sidedness and polarization properties of intrinsically symmetrical relativistic flows and how these effects can be used to estimate the physical parameters of the jets in low-luminosity extragalactic radio sources.

• by R.A.Laing, J.R.Canvin, A.H.Bridle and M.J.Hardcastle
• Monthly Notices of the Royal Astronomical Society, 372, 510-536 (2006)
• Deep imaging with the VLA is used to determine the distributions of spectral index, Faraday rotation measure, and apparent magnetic field over this nearby, low-luminosity radio galaxy.
• The flatter-spectrum radio jets are surrounded by a sheath of steeper-spectrum diffuse emission.
• We apply an intrinsically-symmetrical decelerating relativistic jet model to determine the velocity field of the jets. On-axis, they decelerate from v/c ∼ 0.8 to v/c ∼ 0.4 around 5 kpc from the nucleus with lower velocities everywhere at their edges.
• Our observations rule out a globally-ordered, helical magnetic field configuration but are well modeled by a field that is random on small scales but anisotropic, with toroidal and longitudinal components only.
• We interpret systematic morphological differences between local brightness enhancements ("arcs") in the main and counter-jets as a new effect of relativistic aberration.

• by R.A.Laing, J.R.Canvin and A.H.Bridle
• in "The Origin and Evolution of Cosmic Magnetism", eds. R.Beck, G.Brunetti, L.Feretti and B.Gaensler, Astronomisches Nachtrichten. 327, 523- 526 (2006)
• Large-scale helical fields are incompatible with our VLA polarimetry of the jets in FRI radio galaxies
• The combination of an ordered toroidal and disordered poloidal component is consistent with our data, as is a fully disordered, (but anisotropic) field.
• Jets must also contain small but significant amounts of radial field.

• by R.A.Laing, J.R.Canvin, W.D.Cotton, A.H.Bridle and P.Parma
• in "The Origin and Evolution of Cosmic Magnetism", eds. R.Beck, G.Brunetti, L.Feretti and B.Gaensler, Astronomisches Nachtrichten, 327, 533-534 (2006)
• The fluctuations of the rotation measure are larger in the fainter (receding) jets of two well-resolved FRI radio galaxies, as expected if the rotation occurs in the hot galaxy/group halos and the jet asymmetry is due to relativistic beaming.

• by R.A.Laing, J.R.Canvin, W.D.Cotton and A.H.Bridle
• Monthly Notices of the Royal Astronomical Society, 368, 48-64 (2006).
• Five-frequency imaging with the VLA is used to determine the distributions of spectral index and Faraday rotation measure over the inner ± 400 arcsec of this giant low-luminosity radio galaxy
• The spectral structure suggests a change of dominant particle acceleration mechanism with distance from the nucleus. A transverse gradient from 0.55 on axis to 0.44 at the edge of the jet may be associated with a shear in the jet velocity field.
• The distribution of the Faraday rotation has three components. A constant term and a linear gradient are probably due to our Galaxy. Residual fluctuations are smaller in the brighter (approaching) jet, consistent with the idea that they are produced by magnetic fields in a halo of hot plasma that
• We also image the apparent magnetic field structure of the jets over the first ± 200 arsec from the nucleus.

• by J.R.Canvin, R.A.Laing, A.H.Bridle and W.D.Cotton
• Monthly Notices of the Royal Astronomical Society, 363, 1223-1240 (2005).
• Applies an intrinsically symmetrical decelerating relativistic jet model to deep VLA imaging of the flaring region of the jets in the giant low-luminosity radio galaxy NGC 315.
• The inferred velocity, emissivity and field structure are very similar to those of other low-luminosity sources but all of the physical scales are larger by a factor of about 5.
• Simple adiabatic models fail to fit the emissivity variations.

• by M.J.Hardcastle, D.M.Worrall, M.Birkinshaw, R.A.Laing and A.H.Bridle
• Monthly Notices of the Royal Astronomical Society, 358, 843-850 (2005).
• Observations of the twin-jet radio galaxy 3C296 with Chandra detect X-ray emission from the nucleus, from the inner parts of the radio jet, and from a small-scale thermal environment around the jet deceleration region.
• The X-ray jet and a steep pressure gradient in the external thermal environment are associated with the region where strong bulk deceleration of the jet material is suggested by radio observations.

• by R.A.Laing, J.R.Canvin and A.H.Bridle
• "X-ray and Radio Connections", eds. Sjouwerman, L.O. and Dyer, K.K. (2004)
• Summarizes a project to determine physical conditions in the jets of low-luminosity (FR I) radio galaxies by modeling them as intrinsically symmetrical, relativistic, decelerating flows.
• Derives the three-dimensional distributions of velocity, rest-frame emissivity and magnetic-field structure in the jets. Outlines implications for theories of jet deceleration, including the use of conservation-law analysis to obtain profiles of internal pressure, density, Mach number and entrainment rate along the jets

• by R.A.Laing and A.H.Bridle
• Monthly Notices of the Royal Astronomical Society, 348, 1459-1472 (2004)
• General approach to modeling brightness and polarization structure of adiabatic, decelerating, relativistic jet
• Adiabatic models provide progressively better descriptions of 3C31 jets at larger distances from the galactic nucleus
• Evidence that particles are preferentially injected where bright X-ray emission found

• by D.E.Harris, A. Finoguenov, A.H.Bridle, M.J.Hardcastle and R.A.Laing
• Astrophysical Journal, 580, 110-113 (2002)
• Chandra data show X-ray emission aligned with the northern radio jet
• Synchrotron emission is the favored explanation for the observed X-rays

• by R.A.Laing and A.H.Bridle
• Monthly Notices of the Royal Astronomical Society, 336, 1161-1180 (2002)
• Applies relativistic conservation laws to determine the energy, momentum and mass fluxes in the decelerating jets in an FRI radio galaxy
• Evidence that entrainment from galactic atmosphere is dominant mass input process far from galactic nucleus
• Stellar mass loss may also contribute to deceleration near flaring point of jet
• Compatible with initial electron-positron jet picking up thermal matter from stellar mass loss, or electron-proton jet with low-energy cutoff

• by M.J.Hardcastle, D.M.Worrall, M.Birkinshaw, R.A.Laing and A.H.Bridle
• Monthly Notices of the Royal Astronomical Society, 334, 182-192 (2002)
• Deep Chandra imaging of the X-ray jet and hot gas in and around 3C31
• Derives density, temperature and pressure distribution in atmosphere of host galaxy
• Provides constraints on physical properties and stability of jets

• by R.A.Laing and A.H.Bridle
• Monthly Notices of the Royal Astronomical Society, 336, 328-352 (2002)
• Deep VLA imaging of the jets in 3C31 fitted by models of symmetric, antiparallel, axisymmetric, time-stationary relativistic flows
• Derives jet orientation, velocity field, emissivity variation and magnetic field configuration
• Evidence that jets decelerate by entraining the external medium
• Predicts appearance of jet at range of angles to line of sight, with implications for unified models

• by J.Dennett-Thorpe, P.A.G.Scheuer, R.A.Laing, A.H.Bridle, G.G.Pooley, and W.Reich
• Monthly Notices of the Royal Astronomical Society, 330, 609-620 (2002)
• Multi-frequency radio observations of two winged (X-shaped) radio sources
• Evidence for possible jet axis realignment

• by Christopher Palma, Franz Bauer, William Cotton, Alan Bridle, Steven Majewski and Craig Sarazin
• Astronomical Journal, 119, 2068-2084 (2000)
• radio, optical and X-ray imaging and spectroscopy of a giant radio galaxy at z=0.145
• second largest known FR II radio source, 4 Mpc across
• discovered by the NRAO VLA Sky Survey

• by Jane Dennett-Thorpe, Alan Bridle, Robert Laing and Peter Scheuer
• Monthly Notices of the Royal Astronomical Society, 304, 271-280 (1999)
• correlations between spectral index, jet side and extent of the radio lobes in FR II sources
• hot spot spectra steepen as a function of radio power or redshift

• by Alan Bridle
• Barry Clark at 60, Socorro, June 1998
• imaging NGC315 as an example of the VLA's impact on jet physics

• by Mark Swain, Alan Bridle, and Stefi Baum
• Astrophysical Journal, 507, L29-L33 (1998)
• high-resolution VLA imaging of jet and counterjet in a nearby FR II radio galaxy
• modeling of emissivity and magnetic field distributions within the jet
• evidence that most of emission is from a thick boundary (shear) layer

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• by Jane Dennett-Thorpe, Alan Bridle, Peter Scheuer, Robert Laing, and Patrick Leahy
• untangling intrinsic and apparent asymmetries in synchrotron emission from powerful double radio sources
• Monthly Notices of the Royal Astronomical Society, 289, 753-765 (1997)

• a Workshop held Sept 19-23 1995 at the University of Alabama
• proceedings in A.S.P. Conf. Series, Vol.100 (1996)
• eds. Philip Hardee, Alan Bridle, Anton Zensus

• by Mark Swain, Alan Bridle, and Stefi Baum
• contributed paper in A.S.P. Conf. Series, Vol. 100, pp. 299-304 (1996)
• high-resolution VLA imaging of a nearby radio galaxy
• highest linear resolution ever on a large-scale FR II jet
• evidence for boundary (shear) layer and "sheath" emissions

• by Alan Bridle
• review paper in A.S.P. Conf. Series, vol. 100, pp. 383-394 (1996)
• discussion of jet velocities, velocity fields, and unification
• highlights of observational results presented at the meeting

• by Alan Bridle, David Hough, Colin Lonsdale, Jack Burns, and Robert Laing
• Astronomical Journal, 108, 766-820 (1994)
• sensitive high-resolution radio imaging and polarimetry
• implications for physics of energy transport by jets

• by David A. Clarke, Alan H. Bridle, Jack O. Burns, Richard A. Perley and Michael L. Norman
• Astrophysical Journal, 385, 173-187 (1992)
• High dynamic range VLA images at four frequencies with 1.4-arcsec resolution
• Extended filamentary emission of the lobes
• A second type of filamentation, spatially independent of the total intensity filaments, in the depolarization is associated with strong local gradients in the rotation measure
• Evidence for a clumpy magnetoionic medium around the radio galaxy
• The strengths and weaknesses of two interpretations of the abbreviated jets are considered